The nucleation of semicrystalline polymers with dry particulate materials is well documented. For instance, Jang et al. (J. Polymer Sci. B39:1001 (2001)) used a 4 micron particle size sodium benzoate as a nucleating agent for polypropylene. Ciba Geigy in their commercial literature identify Irgastab NA02 (sodium benzoate with a maximum particle size of 20 microns and mean size of less than 3 microns) and Irgastab NA11UH (a phosphate ester with particle size 6-8 microns). Groeninckx et al. (J. Poly. Sci., Poly. Phys. Ed. 12:303 (1974)) identified that the optimum size for nucleating polyethylene terephthalate (PET) with inorganic particles was 1-3 microns and a volume fraction of 0.2%.